The present invention relates to a contactor having the properties of a circuit breaker whenever shortcircuit currents are generated, comprising, in a housing, two fixed contacts each of which is carried by one leg of a conductor bent in the shape of a U, a rigid contact bridge carrying a movable contact at both extremities thereof, each of said contacts being adapted to cooperate with a fixed contact in register therewith, said bridge being provided, on both sides of its pivoting median portion, with two opposed arms extending in register with said legs, whereas said median portion is so mounted as to slide in said housing from a position of rest at which said bridge is separated from the fixed contacts by an actuating member connected to an electro-magnet armature, to an operating position at which said bridge is applied against said fixed contacts by a resilient member, said contact bridge being capable of occupying a triggerng position farther from said fixed contacts than said position of rest, whenever electro-dynamic repellent forces generated between said arms and legs are above a certain threshold.